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Shiliguri, India

Kejriwal A.,North Bengal University | Bandyopadhyay P.,North Bengal University | Biswas A.N.,Siliguri College
Dalton Transactions | Year: 2015

In biology, aromatic hydroxylation is carried out using a family of heme and nonheme oxygenases, such as cytochrome P450, toluene monooxygenases (TMOs), and methane monooxygenase (MMO). In contrast, a vast majority of synthetic iron based catalysts employed so far in aromatic hydroxylation are monomeric in nature. Herein, we have employed a diferric complex of an aminopyridine ligand ([(bpmen)2Fe2O(μ-O)(μ-OH)](ClO4)3 (2), bpmen = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-diaminoethane) towards aromatic hydroxylation with H2O2 and acetic acid. The diiron(iii) complex shows promising reactivity in the hydroxylation of benzene and alkylbenzenes with a higher selectivity towards aromatic ring hydroxylation over alkyl chain oxidation. The μ-oxo diiron(iii) core has been shown to be regenerated at the end of catalytic turnover. However, mechanistic studies indicate that the diiron(iii) complex undergoes dissociation into its monomeric congener and the resulting iron(iii) complex mitigates aromatic hydroxylation. © The Royal Society of Chemistry 2015.

Pariyar A.,North Bengal University | Bose S.,North Bengal University | Chhetri S.S.,North Bengal University | Biswas A.N.,Siliguri College | Bandyopadhyay P.,North Bengal University
Dalton Transactions | Year: 2012

Selective detection of Hg(II) ions in solution by a series of novel free base bis-(nitrophenyl) corroles (1-4) with general formula A 2B (where A = nitrophenyl, and B = N,N-dimethylaminophenyl, thienyl, naphthyl and tridecyloxyphenyl group) is described. Among the free base corroles, 4, with a tridecyloxy long chain moiety, has been found to exhibit the highest Hg(II) sensing ability. The detection is based on the fluorescence quenching of the corroles, arising from the combined effect of static (coordination) and dynamic (exciplex formation) factors. © The Royal Society of Chemistry 2012.

Bose S.,North Bengal University | Pariyar A.,North Bengal University | Biswas A.N.,Siliguri College | Bandyopadhyay P.,North Bengal University
Journal of Molecular Catalysis A: Chemical | Year: 2013

Metallocorrole catalyzed epoxidation of a series of olefins has been carried out in ionic liquid medium at room temperature with different terminal oxidants. The product selectivity achieved in ionic liquid medium shows remarkable improvement over those obtained in common organic solvents. © 2013 Elsevier B.V. All rights reserved.

Biswas A.N.,Siliguri College | Neogi D.N.,North Bengal University | Das P.,North Bengal University | Choudhury A.,Missouri University of Science and Technology | Bandyopadhyay P.,North Bengal University
Journal of Organometallic Chemistry | Year: 2014

The C2(naphthyl)-H, C3(naphthyl)-H and C8(naphthyl)-H bonds of the naphthyl group present in a group of naphthylazo-2′-hydroxyarenes (H2L) have been activated at room temperature by palladium(II) and stable cyclopalladates of the type [PdL(B)] have been isolated in presence of neutral Lewis bases (B). The activation of C2(naphthyl)-H and C8(naphthyl)-H bonds of 1-(2′-hydroxynaphthylazo) naphthalene (H2L1) lead to the formation of isomeric cyclopalladates 2a & 2b respectively. The single crystal X-ray structures of both the isomers show the naphthylazonaphtholate is coordinated to palladium(II) as a dianionic terdentate C,N,O-donor and Lewis base B occupies the fourth position in the coordination sphere. The ortho-palladate (2a) contains both five-membered carbopalladacycle and azonaphtholato chelate ring whereas a five-membered carbopalladacycle and a six-membered azonaphtholato chelate ring are present in peri-palladate (2b). On the other hand, only C3(naphthyl)-H bond of 2-(2′-hydroxyarylazo) naphthalene (H2L2 & H2L3) has been found to be regiospecifically activated by palladium(II). The role of auxiliary donors on the regioselective and regiospecific C(naphthyl)-H bond activation and the rationale behind the formation of isomeric cyclopalladates have been discussed. All of the cyclopalladates absorb strongly in the ultraviolet and visible region. The Time-dependent density functional theory (TDDFT) calculations reveal that the high energy absorptions are predominantly due to intraligand π-π* and the low energy absorptions originate from intraligand π-π* with a small admixture of metal-to-ligand charge-transfer transitions. © 2014 Elsevier B.V. All rights reserved.

Kejriwal A.,North Bengal University | Biswas S.,North Bengal University | Biswas A.N.,Siliguri College | Bandyopadhyay P.,North Bengal University
Journal of Molecular Catalysis A: Chemical | Year: 2016

Room temperature oxidation of olefins catalysed by a symmetrical (μ-oxo)(μ-hydroxo)diiron(III) complex (1) based on the amino pyridyl ligand bpmen (bpmen = N,N′-dimethyl-N,N′-bis(2-pyridyl methyl)ethane-1,2-diamine) with hydrogen peroxide under the conditions of limiting substrate is described. Excellent substrate conversions have been achieved under ambient reaction conditions. The olefin oxidation efficacy of the 1/H2O2 system has been found to get improved in presence of acetic acid. The catalytic system has been shown to oxidise electron-deficient olefins to the corresponding cis-diols, while epoxidation is favoured in case of electron-rich olefins. The μ-oxo diiron(III) core of the catalyst 1 has been found be regenerated after the catalytic turnovers. Addition of a second batch of substrate and oxidant at the end of the olefin oxidation results in the formation of almost identical amounts of epoxides/diols. Moreover, the regenerated catalyst exhibits a significantly higher preference towards the oxidation of electron-deficient olefins. © 2015 Elsevier B.V. All rights reserved.

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